JS uses the for loop in the function to insert and delete the array at the specified position

           var arr = [10, 20, 30, 40, 50, 60, 70, 80];
			 function del(arr,para){
				for (var i = 0; i < arr.length; i++) {
					if(arr[i]==para){
						break;
					}
					
				}
				console.log(i);
				
				for (var j = i; j < arr.length; j++) {
					 arr[j]=arr[j+1];				
					}
					arr.length--;
					console.log(arr);
			}
			
			del(arr,50); 

           var arr = [10, 20, 30, 40, 50, 60, 70, 80];
           function inser(arr, para1) {
				for (var i = 0; i < arr.length; i++) {
					if (arr[i] == para1) {
						break;
					}

				}
				console.log(i);

				for (var j = arr.length - 1; j > i; j--) {
					arr[j + 1] = arr[j];
				}
				arr[j + 1] = "666";
				console.log(arr);
			}

			inser(arr, 60);